KR100187451B1 - Formation of titanium nitride thin film and film forming device used therefor - Google Patents

Abstract

In the production of a titanium nitride thin film using tetrakis dialkylamino titanium according to the present invention, it is possible to form a film with good coverage even in a hole having a large aspect ratio.

A raw material gas of tetrakis (dialkylamino) titanium is introduced into the reaction vessel 1 by the raw material gas introducing system 4. When the raw material gas is supplied to the substrate 2 previously heated by the holder temperature adjusting mechanism 31, a predetermined thermochemical reaction is caused to produce a thin film composed mainly of titanium nitride.

The pressure in the reaction vessel 1 is controlled by an exhaust system and is maintained to be a predetermined value within the range of 0.1 to 15 Pascals.

Description

Manufacturing method of titanium nitride thin film

The present invention relates to the production of a thin film containing titanium nitride as a main component, which is carried out at the time of manufacturing an electronic device such as a semiconductor device.

(Prior art)

Sputtering, sputtering, chemical vapor deposition (CVD), or the like can be used to produce a thin film such as a diffusion preventing film, a close contact layer film, a wiring film, an insulating film, and a dielectric film which is used when an electronic device such as a semiconductor device, a superconducting device, , A plasma assist method, and a spin coating method have been employed since the past.

2. Description of the Related Art In recent years, as integration of electronic devices, in particular, integration of semiconductor devices, has become high, it has been required to produce thin films having good aspect ratio coverage with contact holes and grooves.

On the other hand, in recent years, there is a strong demand for fabricating a thin film containing titanium nitride as a main component in a semiconductor device. For example, as a manufacturing technique of a contact portion of a semiconductor integrated circuit, in order to prevent mutual diffusion of tungsten for wiring (W) and silicon (Si) as a substrate to obtain stable electric characteristics, titanium nitride is used as a main component between tungsten and silicon Thereby forming a thin film for the diffusion preventing layer.

Alternatively, in order to prevent copper (Cu) of the logic integrated circuit wiring from diffusing into the substrate (Si) or the insulating layer (SiO ₂ ), titanium nitride is used as a main component between copper and silicon or silicon oxide A thin film for the diffusion preventing layer is formed. Then, it is necessary to fabricate a thin film for energization in a through hole provided so as to connect the aluminum film layer of the lower layer and the aluminum film layer of the upper layer as the interlayer wiring technique of the semiconductor integrated circuit. As the conducting thin film, a thin film mainly containing titanium nitride (hereinafter referred to as a titanium nitride thin film) is also used. It has been recently required to fabricate a titanium nitride thin film with good coverage in holes of a high aspect ratio, for example, a contact hole and a through hole.

One of the methods that have attracted attention as a method of producing the titanium nitride thin film with relatively good covering properties is a CVD technique using an organometallic compound or an organic metal complex as a raw material, so-called MOCVD technique.

See, for example, M. Eizenberg et al., Appl. Phys. Lett. 65 (19), 7 November 1994 p. 2416-p. 2418 discloses a method for producing a titanium nitride thin film.

M. Eizenberg et al. Produced a titanium nitride thin film using tetrakis dimethylamino titanium (TDMAT) alone as the raw material at an atmospheric pressure of 0.45 Torr (60 Pa). In the case of a 256 megabit DRAM (occasionally a read-write memory element requiring a memory retention operation), a hole such as a contact hole having a hole diameter of 0.25 mu m and an aspect ratio of 4.0 is formed as a diffusion radiation layer at a coating rate of 90% Is desired.

However, the bottom coverage of the thin film produced by M. Eizenberg et al. Was 85% for the contact hole having a hole diameter of 0.6 탆 and an aspect ratio of 1.5. It is impossible to achieve a coverage rate of 90% in the manufacturing method of M. Eizenberg et al.

Also, Thin Solid Films of Ivo J. Raaijmakers et al. Vol. 247 (1994) p.85-p. 93 describes a method for producing another titanium nitride film.

Ivo J. Raaijmakers et al. Used a source gas (hereinafter referred to as TDMAT-NH ₃ , TDEAT-NH ₃ ) in which ammonia (NH ₃ ) was added to TDMAT or tetrakis diethylaminotitanium (TDEAT) And a thin film is produced. However, Ivo J.Raaijmakers such as the hole diameter was also in a thin film 0.8㎛, with respect to the contact hole of an aspect ratio 1.0 to 20% by TDMAT-NH _3, 85% to TDEAT-NH _3. Even in this case, it is impossible to achieve the requirement of the coverage rate of 90%.

As described above, in the conventional method, when a titanium nitride thin film is manufactured using a source gas containing only tetrakis dialkylamino titanium or a source gas obtained by adding ammonia to tetrakis (dialkylamino titanium), a diffusion barrier layer of a 256 Mb DRAM It is impossible to form the required contact hole with a hole diameter of 0.25 mu m and an aspect ratio of 4.0 at a coating rate of 90%. The present invention has been made to solve such problems, and an object of the present invention is to produce a thin film having good coatability even in a hole having a high aspect ratio in the production of a titanium nitride thin film using tetrakis dialkylamino titanium.

(MEANS FOR SOLVING THE PROBLEMS)

In order to achieve the above object, the present invention relates to a method for producing a thin film comprising titanium nitride as a main component on a mother material having vapor-deposited tetrakis dialkylamino titanium reacted thermally with a high aspect ratio hole as a raw material gas Method. The method is characterized in that the pressure of the atmosphere in which the thermal chemical reaction occurs is set within the range of 0.1 to 15 Pascals in order to improve the coverage of the thin film against the hole in the surface of the base material.

An additive gas is added to the source gas to increase the conductivity of the produced thin film.

Ammonia gas is most suitable as the additive gas. When ammonia gas is added at 15 sccm, the coverage of the bottom of the titanium nitride thin film reaches 100%. As the raw material tetrakis dialkylamino titanium, tetrakis diethyl amino titanium, tetrakis dimethyl amino titanium, tetrakis dipropyl amino titanium, tetrakis di isobutyl amino titanium, or tetrakis ditert-butyl amino titanium are suitable.

(Example)

Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a schematic view of a hot wall type CVD apparatus used in an embodiment of a method for producing a titanium nitride thin film.

The CVD apparatus shown in FIG. 1 has a reaction vessel 1 having an exhaust system 11 and vacuum gages 12 and 13. The reaction vessel 1 comprises a substrate 2 for producing a titanium nitride thin film on the surface thereof, for example, a substrate holder 3 for placing a silicon wafer, and a reaction vessel 1 in which a raw material gas comprising tetrakis dialkylamino titanium And a raw material gas introducing system 4 for introducing the raw material gas.

The substrate holder 3 is provided with a holder temperature adjusting mechanism inside thereof.

And the substrate 2 is heated by the holder temperature adjusting mechanism through the substrate holder 3.

By heating the substrate 2, the raw material gas introduced into the reaction vessel 1 is thermally chemically reacted to produce a titanium nitride film.

The inside of the reaction vessel 1, which is an airtight vessel made of stainless steel, is evacuated by an evacuation system 11. The exhaust system 11 is composed of a rotary pump and a turbo molecular pump. With this configuration, the interior of the reaction vessel 1 is evacuated to about 10 ^-4 Pascals.

As the vacuum gages 12 and 13 for measuring the pressure in the reaction vessel 1, two diaphragm vacuum gages 12 and an ionization vacuum gauge 13 are used. The diaphragm vacuum gauge 12 is a vacuum gauge measuring a high accuracy in the range of about 0.1 to 133 Pascals, for example, Baratron Type 128A manufactured by MKS. A vacuum gauge, for example, BA gauge UGD-1S manufactured by Anerova, is used for the ionization vacuum system 13, which is measured in the range of about 10 ^-2 to 10 ^-6 pascals.

A container temperature adjusting mechanism (14) is arranged on the outer wall surface of the reaction vessel (1).

The container temperature adjusting mechanism 14 includes a heater 141 arranged along the outer wall surface of the reaction vessel 1 and a thermocouple 141 mounted on the outer wall of the reaction vessel 1 for measuring the temperature of the reaction vessel 1 A thyristor unit is used based on the temperature of the reaction vessel 1 measured by the thermocouple 142. The control unit 143 controls the temperature of the reaction vessel 1 A PID control, a PI control, an ON-OFF control, and a purge control for controlling the output current of the power source 143 while controlling the output current of the power source 143. [

The reaction vessel 1 is heated to about 70 占 폚 by the container temperature adjusting mechanism 14 as described above.

The reaction vessel 1 is also provided with a gate valve (not shown) for inserting and withdrawing the substrate 2. [ The substrate 2 on which the titanium nitride thin film is formed passes through the gate valve, enters the reaction vessel 1, and is held in the substrate holder 3.

The substrate holder 3 is provided therein with a holder temperature adjusting mechanism. The holder temperature adjusting mechanism includes a heater 311 embedded in the substrate holder 3, a thermocouple 312 for measuring the temperature of the substrate holder 3, a power source 313 for heating the heater 311 to increase the temperature thereof, A controller 314 for controlling the output current of the power supply 313 while using a control element such as a thyristor unit based on the temperature of the substrate holder 3 measured by the thermocouple 312, -OFF control, and fuzzy control. The substrate holder 3 is heated to about 350 DEG C by the holder temperature adjusting mechanism 31 as described above.

Next, the reaction vessel 1 is set with a source gas introduction system 4, an addition gas introduction system 5, and a carrier gas introduction system 6, respectively. The raw material gas introducing system 4 is composed of a raw material vessel 41 in which liquid Tetrakis dialkylaminotitanium (hereinafter referred to as TDAAT) such as tetrakis diethylaminotitanium (TDEAT) and tetrakis dimethylaminotitanium (TDMAT) And a flow controller 42 for controlling the flow rate of the TDAAT gas and a vaporizer (not shown) for vaporizing the TDAAT, such as a bubbler, a vaporizer, and the like. The raw material container 41 is formed of stainless steel, and its inner wall is electrolytically polished.

The additive gas introducing system 5 comprises a gas tank 51 storing an additive gas such as ammonia gas and a flow controller 52 for controlling the flow rate of the additive gas.

The carrier gas introduction system 6 comprises a gas tank 61 containing a predetermined carrier gas and a flow rate controller 62 for controlling the flow rate of the carrier gas. The mixed gas of the vaporized TDEAT gas and the carrier gas is introduced into the reaction vessel 1 through the pipe 40.

The pipe 40 is not shown so that the vaporized TDAAT is liquefied, but a temperature control mechanism is set.

Next, an explanation will be given of the operation of the CVD apparatus and an embodiment of the method for manufacturing the titanium nitride thin film of the present invention.

First, the substrate 2 is taken into the reaction vessel 1 and held in the substrate holder 3 through a gate valve (not shown), not shown, for transporting robots.

The substrate holder 3 is previously heated to about 350 캜 by the holder temperature adjusting mechanism 31.

Therefore, it can be said that the substrate 2 is also heated to about 350 캜.

On the other hand, the inside of the reaction vessel 1 is exhausted to about 10 ^-4 Pascals by the exhaust system 11. The internal pressure of the reaction vessel 1 during the exhaust is measured by the ionization vacuum gages 12 and 13. After the evacuation, the valve 43 provided in the pipe 40 for introducing the raw material gas and the carrier gas is opened. A mixed gas of TDAAT gas and calorie gas as a raw material gas is introduced into the reaction vessel 1.

At the same time, the valve 53 provided in the additive gas introducing system 5 is also opened to introduce the additive gas into the reaction vessel 1 as well.

The introduced TDAAT gas is heated by the container temperature adjusting mechanism 14 set in the reaction vessel 1 and then further heated on the substrate 2 by the holder temperature adjusting mechanism 31 to generate a thermochemical reaction.

As a result, a titanium nitride thin film is formed on the surface of the substrate 2. When the thickness of the thin film reaches a predetermined value, for example, 200 to 300 angstroms, the valves 43 and 53 are closed to stop the supply of the raw material gas and the additive gas. And the gas remaining in the reaction vessel 1 is exhausted by the exhaust system 11. After evacuating, the interior of the reaction vessel 1 is returned to the atmospheric pressure, and the substrate 2 is taken out of the reaction vessel 1 by the transportation robot.

The pressure in the reaction vessel 1 during the production of the titanium nitride thin film is adjusted by adjusting the TDAAT gas, the carrier gas and the additive gas flow rate to the respective flow rate regulators 42, 52 and 62 so as to fall within the range of 0.1 to 15 pascals. This pressure adjustment is performed by operating the flow rate regulators 42, 52, 53 in accordance with the flow rate conditions corresponding to the pressure within the range of 0.1 to 15 Pascal obtained in advance in the preliminary experiment.

Further, in this preliminary experiment or in the production of the titanium nitride thin film, the pressure in the reaction vessel 1 is measured by the diaphragm vacuum gauge 12. The diaphragm vacuum system 12 constantly monitors whether the pressure in the reaction vessel 1 is within the above-mentioned pressure range during the production of the titanium nitride thin film.

FIG. 2 shows the dependence of the formation rate and the coverage rate on the pressure during the production of the titanium nitride thin film.

The titanium nitride thin film was fabricated on a sapphire wafer in which holes having a diameter of 0.25 mu m and an aspect ratio of 4.0 as a contact hole were formed on the surface. The temperature of the silicon wafer at the time of its fabrication was set at 300 캜.

The flow rate of TDEAT as TDAAT can be set within the range of 0.02 to 0.20 g / min, but it was set at 0.12 g / min during the production. At the time of the production, the flow rate of the nitrogen gas used as the carrier was set to 150 sccm, and the flow rate of the ammonia gas as the additive gas was set to 15 sccm.

In order to set the pressure in the reaction vessel 1, the relationship between the pressure of the mixed gas of the nitrogen gas and the ammonia gas with respect to the desired pressure and the TDEAT gas flow rate is obtained in advance.

Next, nitrogen gas and ammonia gas are introduced into the reaction vessel 1 to adjust opening and closing of a valve (not shown) provided in the exhaust system 11, and set to a pressure lower than a desired pressure according to this relationship . Thereafter, the TDEAT gas set at 0.12 g / min is introduced into the reaction vessel 1 and set at a desired pressure.

In the graph of FIG. 2, the abscissa represents the pressure Pa in the reaction vessel 1 during the thin film production, the left vertical axis represents the bottom coverage rate (%) and the right vertical axis represents the film formation rate (m / min).

The bottom coverage rate , The film formation rate is .

As shown in FIG. 2, at a pressure lower than 0.1 Pascal, the film-forming speed is remarkably low, making it difficult to adopt it for practical use. In addition, at a pressure exceeding 15 Pascal, the coating rate of the bottom portion is extremely lowered, and it is unsuitable for forming a film on a hole having a high aspect ratio such as a contact hole. The same result was obtained when TDMAT was used as the TDAAT. The same results were also obtained when tetrakis (dipropyl) amino titanium, tetrakis diisobutyl amino titanium, and tetrakis ditert-butyl amino titanium were used as TDAAT.

Since these TDAATs are solid at room temperature and normal pressure, when these TDAATs are used in the production of a titanium nitride thin film, they are dissolved in a solvent such as hexane to prepare a liquid raw material.

From these experimental results, it is found that, when the titanium nitride thin film is produced by using TDAAT, the film formation is carried out in the pressure range of 0.1 to 15 Pascal at a high coating rate and at a high film formation rate As shown in FIG.

This result confirmed the validity of the pressure condition even when the flow rate of the raw material gas varied within the range of 0.02 to 0.20 g / min. Under such a pressure condition, the reason why the high coverage rate of the disease titanium thin film can be made at a high speed is considered as follows.

That is, when the pressure is low, the source gas is not sufficiently supplied to the substrate 2, and thus the film formation rate is delayed. Further, in the case of a high pressure exceeding 15 Pascal, it is considered that an active intermediate having a high adhesion probability to the surface of the substrate is generated in the space in front of the substrate. The intermediate is attached to the surface of the substrate or the side wall of the hole before reaching the bottom of the hole.

The probability of reaching the bottom of the hole of this intermediate is lowered, and as a result, the coverage rate deteriorates. When the pressure is lowered to 15 pascals or less, the generation of intermediates having such a high adhesion probability is suppressed, and a substance having a low adhesion probability is produced in large quantities.

These materials have a high probability of reaching the bottom of the hole, and consequently, the coverage rate of the hole is considered to be high.

FIG. 3 shows the dependence of the film formation rate, the bottom coverage rate and the resistivity on the flow rate of the ammonia gas as the additive gas. The abscissa of the graph in FIG. 3 represents the flow rate (sccm) of the ammonia gas, the ordinate on the right side represents the film formation rate (nm / min), and the ordinate on the left side represents the coverage percentage (%) and resistivity (占 ㎝ m). The film formation rate is , The bottom coverage rate , And the resistivity is indicated by?.

The titanium nitride thin film was formed on a silicon wafer having a contact hole having a diameter of 0.25 mu m and an aspect ratio of 4.0 formed at a temperature of 300 DEG C under a pressure of 6.7 Pa.

The flow rate of TDEAT as TDAAT was set at 0.12 g / minute at the time of the production and the flow rate of the nitrogen gas used as the carrier at 150 sccm.

The flow rate of the ammonia gas is 15 sccm, and the coverage rate of the bottom portion reaches 100%.

Further, in the case of adding the ammonia gas at the flow rate? _{S of} 5sccm, the resistivity is reduced to about 10,000 占 占 ㎝ m compared with the case where the ammonia gas is not added at about 24,000 占 ㎝ m. Even when the flow rate of the ammonia gas is 15 sccm or more, the ammonia gas remains constant at about 10,000 占 cm. With respect to the film formation rate, the film was abruptly increased to about 16 nm / min when ammonia gas was added at a flow rate of 15 sccm when ammonia gas was not added, to about 2 nm / min. Also, when the flow rate of the ammonia gas is increased to 15 sccm or more, the film formation rate is gradually increased. The ammonia gas used as the additive gas in the above embodiment is intended to improve the conductivity of the titanium nitride thin film to be produced.

In the case of preparing a thin film by adding ammonia gas, when the ammonia gas is 15 sccm in a pressure range of 0.1 to 15 Pa, a bottom coverage rate of 100% is achieved.

1 is a schematic view of a CVD apparatus used in the embodiment of the present invention, FIG. 2 is a graph showing the dependency of the film formation rate and the bottom coverage ratio on the pressure during the production of the titanium nitride thin film, And the dependency of resistivity (resistivity) on the film formation rate, the bottom coverage rate and the flow rate.

DESCRIPTION OF THE REFERENCE NUMERALS

1: Reaction vessel 11: Exhaust system (Haiku system)

12: ionization vacuum gauge 13: diaphragm vacuum gauge

14: container temperature control mechanism 2: substrate (substrate)

3: substrate holder 31: holder temperature adjusting mechanism as heating means

4: feed gas introduction system 5: additive gas introduction system

As described above, according to the titanium nitride manufacturing method of the present invention, a thin film is formed at a high film forming rate with respect to a contact hole having a large aspect ratio, and a thin film having a high coating ratio is formed with respect to a hole having a large aspect ratio. Addition of ammonia gas also achieves coverage rate of 100%.

Claims (5)

Vaporized tetrakis (dialkylamino titanium) as a raw material gas is thermally chemically reacted in an atmosphere having a pressure within a range of 0.1 to 15 Pascals, thereby depositing a thin film containing titanium nitride as a main component on the surface of the substrate. The method for producing a titanium nitride thin film according to claim 1, wherein another gas is added to the raw material gas. The method for producing a titanium nitride thin film according to claim 2, wherein the added gas is an ammonia gas. 4. The method for producing a titanium nitride thin film according to claim 3, wherein an ammonia gas is added to the source gas at a flow rate of 15 sccm. The method according to claim 1, wherein the raw material tetrakis dialkylamino titanium is at least one selected from the group consisting of tetrakis diethylaminotitanium, tetrakis dimethylaminothitan, tetrakis dipropylaminothiotin, tetrakis diisobutylaminothiotin, A process for producing a titanium nitride thin film characterized by being a bichatic amino titanium